Hydraulic fuse



J. M. KING HYDRAULIC FUSE Nov. 8, 1949 2 Sheets-Sheet 1 Filed July 9,1941 Nov. 8, 1949 J. M. KING 2,437,955

HYDRAULIC FUSE Filed July 9, 1941 2 Sheets-Sheet 2 INVENTOR ATTORNEYSPatented Nov. 8, 1949 HYDRAULIC FUSE John M. King, Dover, N. J assignorto the United States of America as represented by the Secretary of WarApplication July 9, 1941, Serial No. 401,584

(Granted under the act of March 3, 1883, as amended April 30, 1928; 3700. G. 757) 6 Claims.

The invention described herein may be manufactured and used by or forthe Govermnent for governmental purposes, without the payment to me ofany royalty thereon.

This invention relates to a hydraulic fuse, and more particularly to afuse for aerial drop bombs which will fire upon impact with solidsurfaces or at predetermined depths after striking water.

In carrying out bombing operations from aircraft over water, it isdesirable to employ a fuse which will permit selective settings for thevarious depths at which the fuse will operate. Likewise it is importantthat there be incorporated in the fuse, detonating elements which willfunction instantaneously or with a short time delay when the missilestrikes the ground or some solid object.

In accordance with a preferred embodiment of the invention, the fuse isprovided with an expansible fluid chamber which is actuated bypredetermined hydraulic pressures when the bomb is dropped into waterand also an inertia device which fires a delay primer-detonator when themissile strikes a solid objective.

An object of the invention is to provide a fuse for a drop bomb whichwill function when it 1 strikes water or a solid surface.

Another object of the invention is to provide a detonating fuse whichwill fire upon impact with a solid objective or at predetermined depthsafter impact with water.

A further object of the invention is to provide a fuse which issafeguarded from accidental operationduring handling and shipment.

The specific nature of the invention as well as other objects andadvantages thereof will clearly appear from a description of a preferredembodiment as shown in the accompanying drawings, in which:

Fig. 1 is a front elevation of the fuse,

Fig. 2 is an enlarged vertical longitudinal sectional view of the fuseshowing details of construction,

Fig. 3 is a section on the line 3-3 of Fig. 2 showing the equalizermountings,

Fig. 4 is a sectional view on the line 4--4 of Fig. 2 showing the depthsetting mechanism,

Fig. 5 is an enlarged front elevation of a port1on of the fuse whenforced into the firing position by hydraulic pressure,

Fig. 6 is a sectional view on the line 6-6 of F1g. 2 showing the Sylphonbellows locked in the inoperative or safety position,

Fig. 7 is a sectional view on the line l--! of Fig.2,and s Fig. 8 is aview in axial section of the pressure disk and its associated pinshearing sleeve.

Referring to the drawings by numerals of reference, the metal fuse body8 is threaded at 9 to engage the base of a shell or tail of a bomb. Ahollow protuberance l0 extends into the shell and carries a firing pinII, which when actuated, engages the primer I2 and detonates the shell.

A cylindrical block l3 has a central bore l4 and is in threadedengagement at I5 with the body 8. See Figs. 2 and 3. The lower end ofthe block l3 has a threaded skirt I6 which engages an annulus H which inturn engages a threaded plate closure l8. The plate I 8 has an extensionl9 and carries a primer 20 which includes a five second delay primerdetonator 2i.

Fastened to the extension H! by suitable means is a sleeve 22 having aback plate 23. Within the sleeve 22 is a sliding metal plunger 24containing at its front end a firing pin 25 facing the primer 20. Acoiled spring 26 keeps the plunger and firing pin separated from theprimer 20 except under certain conditions which will be discussed later.A headed locking pin 21 passes through apertures in the plunger 24 andthe sleeve 22 as shown in Fig. 2. A spring 28 encompasses the pin 21 andis compressed between the head 29 and the sleeve 22 and the assembly islocked in position by the release pin 30.

Block I3 is annularly grooved at 3| and riding in the groove is arotatable setting ring 32. Ring 32 carries opposed fins 33 which restsin annular channels 34 in the fuse body 8 and the block l3. Packingmaterial 35 is employed to seal the joints between the fins 33 andchannels 34 to make this portion of the fuse water-proof.

A cup-shaped cylinder 36 (see Fig. 5) rests with its flanged end 3! onthe body 8 and the perforated opposite end 38 engages the open end of acylinder 39 containing a tetryl charge 40. The lower end of cylinder 39is threaded into the central portion of plate l8 and communicates withthe primer detonator 2 I. A hollow plunger 4| having a tapered nose 42slides in the cup 36. One end of the firing pin II is threaded into thenose of the plunger 4|. Seated in the hollow plunger is a coiledcompression spring 43 which also bears against the base of the cup 36.The side wall of the cup 36 is pierced by a pair of apertures 44 whichreceive steel locking balls 45.

In the armed position a steel sleeve 46 surrounds the cup 36 coveringthe apertures 44. The sleeve 46 also encloses a portion of the tetrylcharge containing cylinder 39 and is free to slide bsqlswardly in borel4 on both the fixed cup 36 and the charge container 39. The upper endof the sleeve 46 has an annular enlargement 41 with a tapered upper face48 and a right angle annular shoulder 49 as shown in Fig. 8. The lowerend of the sleeve 46 carries an annular groove 50.

A rigid pressure disk having a perforated cylindrical side wall 52 iscontained in a chamber 53 and is centrally clamped in the groove 50 ofsleeve 46. The side wall 52 is shallower than the depth of chamber 53.An expansible fluid chamber 54 is formed by "the use of a pair ofSylphon bellows 55 and 56. The inner bellows 55 has one end clamped inthe annular groove 50 in sleeve 46 and forms a fluidtight seal. Theother end is brazed or soldered to the block |3 near the edge of borel4. The lower end of the outer bellows 56 is brazed to the disk 5| andthe upper end is securely clamped between the skirt l6 of block I3 andthe ring IT. This provides a fiuidtight expansion chamber 54.

The skirt l6 of ring I13 has a plurality of apertures 5'! which serve asfiuid ports and permit water to enter the expansible chamber 54. Asafety pin 53 is insertable in one of these ports 57 and has its innerend 59 conditioned to engage one of the apertures in the wall 52 of thepressure disk 5|. This prevents movement of the disk 5| and associatedmovable elements and negatives the danger of accidental firing, in amanner to be described, during handling of the fuse.

Block I3 is provided with a plurality of radially disposed bores 6twhich terminate in restricted inner passages of unequal diameters. Shearpins 6! having enlarged heads 62 rest in these bores and carrycompression springs 63. pins are restrained by ring 32 against whichthey are forced by the springs 63. Each shear pin has a differentdiameter and is selected to shear when a predetermined forcecorresponding to a hydrostatic pressure at a definite depth .is appliedI transversely to the length of the pin. Six pins are employed and fivemay be selectively presented to be sheared at depths in the order often, twenty, thirty, forty, andyfifty feet. The remaining pin isovers-ized and will not be sheared. When cammed inwardly it represents asafety stop for the moving elements.

The inner periphery of the rotary setting ring 32 is provided with fivespaced recesses 64 to receive the ends of the heads-62 of the shear pins6 I. See Fig. 4. The axis of the bore of ring 32 is eccentric to that ofthe block |3 which carries the shear pins 6|. When the ring 32 isrotated to a selected position so that five of the pins 6| are lodged inrecesses 64, a high spot 65 engages the sixth pin and forces it inwardlyagainst the resistance of its spring 63. This pin is conditioned to besheared by the shoulder 49 on sleeve 46 as shown in Fig. 2. The ring 32and the body 8 of the fuse are graduated as shown in Fig. 1 to indicatethe pin to be sheared at the selected depth.

To counteract the forces of deceleration on the moving parts of the fuseupon water impact, an equalizer is employed. The equalizer comprises apair of fiyweights 66 on arms 61 which are attached to pivot pins 68 asshown in Figs. 2 and 3. Pins 68 are mounted in the circular block orring I3. On the side of each pin 68 opposite the flyweight 66 is aprojection 68 having a tapered face. This projection 69 is in engagementwith the angular enlargement 4'! on the sleeve 46.

The shear The operation of the fuse is as follows: Before the drop bombis inserted in the bomb suspension of an aeroplane, the safety pin 58 isremoved from the fuse to permit the operation of the hydraulicmechanism. When the bomb is released, the pin 30 is withdrawn by thesafety wire of the release mechanism. Compression spring 28 expands andwithdraws the safety pin 21 to free the plunger 24 which is held in itsinoperative position by spring 26.

Should the bomb strike a solid target, the

- plunger 24 is influenced by-inertia and moves forward :the sleeve 22against the resistance of the spring 2.6 whereupon the firing pin 25strikes the primer 2.0 and fires the delay primer detonator .21. This inturn fires the tetryl charge 40 which forces the plunger 4| carrying thefiring pin H past the retaining balls 45 and into the primer l2 anddetonates the shell.

When the bomb falls into water and the hydrostatic mechanism fails tooperate, the plunger 24 actuates the firing pin as described above anddetonates the shell, thus assuring certainty of function.

Upon landing in water, fluid enters the expansible chamber 54 throughthe water ports 51. As the bomb sinks below the surface, the hydrostatichead increases and the pressure on the disk 5| is directly proportionalto the head. Pressure of the disk 5| is communicated to the attachedsleeve 46 and force is applied by the shoulder 49 to a pin 6| which waspreviously indexed into the shearing position by the setting ring 32. Ifthe fuse was set to operate the firing rod H at a fifty-foot depth, thepin 6| corresponding to that setting will be sheared by the shoulder 49on sleeve 46' by the fluid pressure existing at that depth. When thisoccurs the disk 5| strikes the wall of closure |8 as shown in Fig. 5 andthe free end of sleeve 46 slides beyond its zone of influence on theretaining balls 45. The tapered face 42 of the plunger 4| forces theseballs later- :ally in the recesses 44 because of the force exerted bycompression spring '43, and also forces the now released firing pin intothe primer I2 and the bomb is exploded.

As the bombis sinking beneath the surface of the water, decelerationtakes place because of the added resistanceto its movement. Inertiabegins to act upon the movable disk 5|, the bellows mechanism 55 and516, and the sliding sleeve 46. Its effect is to pull this movablemechanism forward in opposition to the force exerted rearwardly by theincreasing hydrostatic force which is being applied to the shear pin 6|.To compensate for this undesirable effect, the fiyweights 6B are rotatedabout the pins 68 by the effect of inertia upon deceleration.Theextensions 69 on the opposite side of the pivot pins 68 are forcedback on the shoulder 48 on sleeve 46 and exert a counterbalancing forcefor the effect of inertia on the movable pressure system. The pin 6| istherefore sheared at the correct predetermined depth.

I claim:

1. A fuse for a depth bomb comprising a body having fluid ports, anormally armed firing pin in said body, a way for said pin, acompression spring for driving said pin when the pin is released, afluid pressure operated member in said body adjacent said ports, a latchon said way to retain said firing pin in the armed position, selectivedepth setting mechanism in said body in latching engagement with saidpressure member, said mechanism including shear pins of different shearresistance and a selecting ring, one of said pins adapted to be shearedby a hydrostatic head on said pressure member at a predetermined depthto release said latch and firing pin.

2. A fuse for a depth bomb operable alternatively on water or heavyimpact comprising a perforated body, a normally armed firing pin in saidbody, a way for said pin, a compression spring for driving said pin whenthe pin is released, a fluid pressure operated member in said body, alatch on said way to retain said firing pin in the armed position,selective depth setting mechanism in said body in latching engagementwith said pressure member, said mechanism including shear pins and aselecting ring, one of said pins adapted to besheared by a hydrostatichead on said pressure member at a predetermined depth to release saidlatch and firing pin, and an inertia firing mechanism to releaseforceably said latch and firing pin on heavy impact.

3. A fuse for a depth bomb operable alternatively on water or heavyimpact comprising a perforated body, a normally armed firing pin in saidbody, a way for said pin, a compression spring for driving said pin whenthe pin is released, a fluid pressure operated member in said body, alatch on said pressure member to retain said firing pin in the armedposition, selective depth setting mechanism in said body in latchingengagement with said pressure member, said mechanism including shearpins and a selecting ring, one of said pins adapted to be sheared by ahydrostatic head on said pressure member at a predetermined depth torelease said latch and firing pin, and an inertia firing mechanismhaving a delay action to release forceably said latch and firing pin onheavy impact.

4. A fuse for a depth bomb operable alternatively on water or heavyimpact comprising a perforated body, a normally armed firing pin in saidbody, a way for said pin, a spring for driving said pin when the pin isreleased, a fluid pressure operated member in said body, a latch on saidpressure member to retain said firing pin in the armed position,selective depth setting mechanism in said body in latching engagementwith said pressure member, said mechanism including shear pins and aselecting ring, one of said pins adapted to be sheared by a hydrostatichead on said pressure member at a predetermined depth to release saidlatch and firing pin, a deceleration compensating lever of the firstorder pivoted to said body, a flyweight on one end of said lever and theother end engaging said pressure member, and an inertia firing mechanismto release forceably said latch and firing pin on heavy impact.

5. A fuse for a drop bomb comprising a body, a cylindrical blocktherein, a firing mechanism within said body, an expansible fluidpressure means within said body, selective depth setting means mountedin said body and including a plu rality of shear pins of different shearresistances, respectively, said shear pins being slidably mounted insaid cylindrical block and selectively moved into association with saidexpansible fluid pressure means for causing the same to maintain saidfiring mechanism inoperative, said expansible fluid pressure meanshaving an annular shoulder cooperating with said cylindrical block andmovable relative thereto by expansion of said fluid pressure means forshearing the shear pin selectively moved into association with saidexpansible fluid pressure means whereby the same will release saidfiring mechanism for operation.

6. In a fuse for a drop bomb, the combination of a body, a cylindricalblock therein, a firing mechanism within said body, a fluid pressuremechanism within said body, a plurality of shear pins of difierent shearresistances, respectively, slidably mounted in said cylindrical blockand selectively moved into association with said expansible fluidpressure means for causing the same to maintain said firing mechanisminoperative, a camming ring means rotatively mounted on said body andencompassing the said cylindrical block, spring means biasing said shearpins against said ca/mming ring means whereby the same can selectivelymove one of said shear pins into association with said expansible fluidpressure means, said expansible fluid pressure means having an annularshoulder relatively movable with respect to said cylindrical block byexpansion of said fluid pressure means for shearing the shear pinselectively moved by said camming ring whereby said expansible fluidpressure means will release said firing mechanism for operation.

JOHN M. KING.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 431,374 Merriam July 1, 18901,314,663 Huber Sept. 2, 1919 1,368,569 Minkler Feb. 15, 1921 1,415,614Sperry May 9, 1922 1,534,126 Lucas et a1 Apr. 21, 1925 1,639,665 PrattAug. 23, 1927 1,943,706 Varaud Jan. 16, 1934

